Classes of perfluoralkylcarbonyl fluorides containing straight chain perfluoroalkyl groups, cyclic perfluoroalkyl groups, and derivatives thereof are known. U.S. Pat. No. 2,567,011 (Diesslin et al.), for example, describes fluorocarbon carbonyl fluorides, monocarboxylic acids, and their derivatives containing open-chain (i.e., non-cyclic) and closed-chain (i.e., cyclic) perfluoroalkyl groups, and combinations of cyclic and non-cyclic fluorinated alkyl sub-radicals. All open chain structures cited by Diesslin et al. are straight chain structures (e.g., CF.sub.3 (CF.sub.2).sub.n --); no branched open chain structures are noted.
U.S. Pat. No. 3,351,644 (Hauptschein et al.) describes straight-chain telomeric acid fluorides of the structure R.sub.f (CF.sub.2 CF.sub.2).sub.n COF, where R.sub.f is a perfluoroalkyl or monochloroperfluoroalkyl group and where n is a small number from 1 to about 8.
British Amended Patent 1,092,141 describes perfluoroalkylcarbonyl fluorides containing omega (.omega.)-branched perfluoroalkyl chains, i.e. of the structure (CF.sub.3).sub.2 CF(CF.sub.2).sub.n --. These .omega.-branched perfluoroalkylcarbonyl fluorides reportedly are produced as a minor component during electrochemical fluorination of straight chain hydrocarbon carbonyl fluorides and derivatives.
U.S. Pat. No. 4,749,526 (Flynn) describes .alpha.-branched perfluoropolyether carbonyl fluorides having the general formula R.sub.f CF.sub.2 O[CF(CF.sub.3)CF.sub.2 O].sub.p CF(CF.sub.3)COF. Acids derived from these materials have been shown to be stable to decarboxylation of the perfluoropolyether chain.
Short-chain .alpha.-branched perfluoroalkylcarbonyl fluorides and acids and certain classes of short-chain cyclic group-containing .alpha.-branched perfluoroalkylcarbonyl fluorides are known. Gambaretto et al. (Chim. Ind., 1971, 53, 1033-8) reports the preparation of C.sub.4 F.sub.9 CF(C.sub.2 F.sub.5)CO.sub.2 H and (CF.sub.3).sub.2 CFCO.sub.2 H by electrochemical fluorination and the subsequent decarboxylation of these acids. The electrochemical fluorination of .alpha.-alkyl-substituted acid chlorides and methyl esters to give perfluorooxolanes and perfluorooxanes as well as a small amount, i.e. nine percent, of the corresponding perfluoroalkanoyl fluorides (e.g. C.sub.5 F.sub.11 CF(CF.sub.3)COF) also has been reported. (Abe, T. et al., J. Fluorine Chem., 1978, 12, 1-25). In this article, Abe et al. also reports the existence of C.sub.4 F.sub.9 CF(C.sub.4 F.sub.9)COF.
Certain cycloalkyl group-terminated .alpha.-branched perfluoroalkylcarbonyl halides are known. c-C.sub.6 F.sub.11 CF.sub.2 CF(CF.sub.3)COF has been reported (T. Abe et al. in Chapter 1 of "Preparation, Properties, and Industrial Applications of Organofluorine Compounds," R. E. Banks, editor, Ellis Horwood Ltd., Holsted Press (1982)), and c-C.sub.5 F.sub.9 CF(CF.sub.3)COF and c-C.sub.5 F.sub.9 CF(C.sub.2 F.sub.5)COCl (Abe, T. et al., J Fluorine Chem., 1983, 23, 123-146) have been disclosed.
Straight-chained perfluorocarboxylic acids of the structure R.sub.f CF.sub.2 COOH and derivatives thereof are known not to degrade under aqueous environmental exposure and do not thermally decarboxylate until at least 180-200.degree. C. (J. Am. Chem. Soc., 1953, 75, 4525-28). These compounds are very stable and, therefore, also persist in the environment. It is also known that linear perfluorocarboxylic acids and their carboxylate salts are moderately toxic, especially longer chain salts such as n-C.sub.9 F.sub.19 COO.sup.- NH.sub.4.sup.+. (See, e.g., Goeche-Flora et al., Chem. Res. Toxicol. 1996, 9, 689-95).
While it is known that fluorochemical acids of the type (R.sub.f).sub.2 CFCO.sub.2 H, where R.sub.f is a short chain such as CF.sub.3 and C.sub.2 F.sub.5, are unstable in aqueous solution (See, e.g., Chim. Ind., 1971, 53, 1033-8), these compounds generally possess poor surfactant properties.
There are no known fluoroalkylcarbonyl fluoride derivatives that exhibit a combination of those properties that are favorable in today's chemical market. A highly desirable fluorochemical compound is one having superior surfactant properties when dissolved in a liquid (i.e., can reduce the surface tension of the liquid to a value lower than 20 dynes/cm), is relatively non-toxic or is very low in toxicity, and is non-persistent in the environment (i.e., can completely degrade biochemically, thermally, or photochemically under mild conditions such as those encountered in the environment under ambient conditions).